The present invention relates to a method and apparatus for automatically grinding the sliding surface of a skate to a desired profile with regard to at least two dimensions x and y in a coordinate system, in which a rotatable grinding wheel is movable in x-direction along the length extension of the sliding surface and in y-direction in an angle thereto by means of guiding means.
Advanced skaters and experts have found that the individual skate-style demands a particularly formed sliding surface for the skates. The sliding surface can be regarded as a grind profile--the outer contour of the sliding surface in a lateral view--and as the grind cross section--the sliding surface in a section from the front. Grind profile and grind cross section do not need to by symmetrically equal for right and left skate. It has also recently been discovered, that the sliding effect of the skate increases if a straight sliding surface is ground in existing grind profile. Thus, the sliding surface for each skater, particularly professional skaters is unique, and demands extensive experimental work to be found out by experiment.
Particularly in connection with ice-hockey, bandy and speed-skating, it hs been discovered, that the sharpening degree of the sliding surface is of importance for the sliding resistance of the skate, for example a too sharp sliding surface yields partially high contact pressure which tends to deform the ice in a way unfavourable for the sliding resistance. This deformation depends of course on the hardness of the ice but above all on the force that the skater develops during the skating.
When a skater has discovered the grinding best suited to his skating and the ice surface, it is of greatest importance, that the grind profile and the grind cross section be maintained when resharpening the skate slide surface.
Skate grinding presently demands an expert who manually grinds the sliding surface of the skate. For grinding a straight sliding surface a number of "planning models" having different long straight surfaces exist. The exact grind profile is impossible to obtain or maintain. A sliding surface as individually formed as possible can with this manual method be produced today.
U.S. Pat. No. 3,735,533 discloses an automatically operating grinding or sharpening machine for skates. This machine is, however, only manufactured as a coin-operated automatic machine for grinding two skates after the correct number of coins has been inserted into a coin-mechanism. The machine is very comples, since it requires a multitude of controls. It can nevertheless only grind in accordance with a fixed program and performs only hollow grinding (concave cross-section). The number of times the grinding wheel performs depends upon which switch has been selected, "good", "fair" or "poor" and that a correct number of coins has been inserted. The grinding direction is always the same.
The main object of the present invention is to provide a technique which allows an automatically performed mechanical sharpening of a skate slide surface as well as controlled individual change of grind profile and/or cross-section of the skate.
Another object of the invention is to provide a method which provides optional detailed configuration of grind profile and grind cross-section.
A further object of the invention is to provide a method for maintaining a successful sliding surface through repeated sharpening.
Still another object of the invention is to provide a method for changing the skate grind profile with regard to the positioning of a desired straight sliding surface with minimum machining grinding on the skate blade.
Still another object of the invention is to provide a method that can be used over a long period of time without service with continued acceptable capability to sharpen and change the grind profile/grind cross-section of the skate blade.
Compared to the above mentioned known automatic skate sharpening machine the method and apparatus according to the present invention is essentially simpler and moreover all the different kinds of grinding, as individually desired, can be performed by the invention. The only requirement is to position the skate in an skate holder and thereafter start the grinding cycle via a manual starting device or, if the apparatus, according to the invention, should be constructed as a coin operated apparatus, a coin-accepting device. Thereupon, the existing profile of the skate blade is scanned. At the same time a recording of the measured x- and y-values takes place continuously in a memory, preferably an electronic memory, from a 0-position, which is the position where the grinding wheel, used for scanning first contacts the skate blade after movement in the y-direction from its starting position. From the 0-position, the grinding wheel is moved only in a contacting state without grinding during recording of the x- and y-values in the memory, and then returns to the 0-position. After correction of the measured x- and y-values in the memory to the desired profile, the grinding wheel is put into rotation and guided during grinding of the skate sliding surface with adequate machining (0.05-0.1 mm) along the path determined by the prerecorded corrected x- and y-values. A total grinding cycle to achieve the desired grinding profile can include several grindings with appropriate machining for each. The number of grindings can be choosen in advance.
The invention also provides for possible grinding of at least one straight slide surface along a part of the profile. This straight slide surface can optionally be positioned along the profile. The grind profile recorded in the memory is completed with at least two x-values (x1 and x2) from the 0-position using for instance a keyboard. The grinding takes place according to the recorded x- and y-values with the exception that the grinding wheel grinds along the shortest distance between the completed x-values. The number of grindings can be adapted so that machining to the desired grind profile (x, x1, x2, y) is obtained.
In addition to ordinary symmetric grind cross-section obtained by hollow grinding, the invention provides for displacement of the grinding in the z-direction of the coordinate system and accordingly an unsymmetrical grind cross-section is obtained, which is suited to certain skaters' skating style. Such a displacement is obtained in a simple way by arranging the grinding wheel to adjust in the z-direction.
The method according to the invention also provides for storage of an individual grind profile which can, for instance, be recorded on magnetic tape, for repeated use.
It is evident from the above discussion evident, that the method and apparatus according to the invention can be made more or less advanced. In one embodiment the x- and y-coordinates are recorded during scanning of the existing profile and the grinding takes place in accordance with this recording after correction to the desired profile. It is also possible to allow the apparatus to suggest a specific grind profile. In another embodiment the method of the invention also allows for guiding of the grind process with regard to the grind cross-section. Moreover, the invention provides for storage of the previously obtained desired grind profile for future repeated grinding.